Half-life time

Physical half-life time (Tp)

The time interval required for an amount of certain radioactive nuclei to decay to half of its original value.

Biological half-life time (Tb

The time interval required for the body to eliminate 50% of any substance by normal routes of elimination: metabolic turnover and excretion.

Effective half-life time (Te)

The time interval required for the radioactivity of a certain amount of radioactive substance distributed in tissues and organs to decrease to half its original value due to radioactive decay and biological elimination.

The physical half-life time > biological half-life time > effective half-life time.

1/Te = 1/Tp+1/Tb

Imaging physics
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Article information

rID: 16435
Synonyms or Alternate Spellings:
  • Effective half-life time
  • Biological half-life time
  • Physical half-life time
  • Half life

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